I’m not a meteorologist and I don’t play one on TV.
Even if you can't do anything about El Nino or the rest of our weather, you can talk about it. Click here.
Oh, I grew up wanting to be one. When I was a gawky kid in Arkansas, I got a reputation in elementary school for being able to out-forecast the local TV weatherman, who was really just an often-tipsy DJ and bad comedian. I grew up on a steady diet of tornado warnings -- and those of you from the Midwest know about those times when the television is nothing but weathermen for hours pointing at hook echoes while the news reporters chase disappearing subdivisions. I saw SIX tornadoes myself between 1974 and 1999. Darn near drove into one.
But the Lord had other plans for me, as newspaper things just started happening. Like "accidentally" having to take a journalism class my sophomore year of high school when other classes were full. Like having a sportswriting job fall in my lap days after my high school graduation. Like trying my hardest once to leave newspapers behind once and for all only to have a small-town newspaper publisher offer me an editor job at a bank parking lot. The newspaper life is a calling. I could more easily run from twisters than from the ink in my blood.
This career turn was all for the better for me. Though meteorologists have been glamorized in recent years by the movie "Twister" and by being labeled the "sexiest men" of certain cities, the more likely destination for someone with a degree in meteorology is sitting behind a radar screen in a windowless office in Sioux Falls, South Dakota.
Don’t get me wrong: These folks are often heroes, right next to firemen and policemen. If you don’t believe that, compare tornado fatality figures between the last 10 years with any 10-year period before 1960. Those nameless faces looking for clashing colors on a Doppler radar screen are saving lots of lives. But I like to be outside more. That’s probably why I took up hiking. (See my hiking page on roanoke.com)
As a journalist and editor for 14 years, I got to write plenty about weather events and lots of other memorable things, too. But my passion for weather still stalks me, and finally caught up with me here in Roanoke. I got myself labeled as the newsroom weather geek -- or "weather guru" as What’s On Your Mind columnist Tom Angleberger somewhat mystically calls me. Even after I moved to advertising in the fall, I’ve still been an unofficial weather consultant. And now, they’re giving me a column online.
So what the heck is this all about? The truth is, whatever I want it to be. We’re going to talk about the weather -- we’re not going to do anything about it, we’re just going to talk about it. Past, present and future weather. This site will evolve into whatever we want to make it. And largely whatever you want us to make it.
I’m sure I’ll be hearing from some of you as the days go along. There’s something of a weather geek in almost all of us.
As a certified weather geek, I patrol weather sources on the Internet that normal folk fear to tread. Or rather, don’t know to tread. Or rather, don’t’ care to tread. Or rather, don’t know exists. Twice a week, on Tuesdays and Fridays, and more often when weather events warrant, I’ll attempt to boil some of this down for you, with a little fun and flavor.
Obviously, we didn't get accumulating snow Sunday. The pieces didn't quite come together to make it happen. The Ohio Valley got heavier than expected snows out of a southeastward moving "clipper" system and one little system squirted just south of us out to sea. If these two had got together, today would be a lot of whiter. Instead, all we got was the last reinforcing shot of this Arctic air mass that's been plaguing us for nearly three weeks.
While the pure Arctic air will modify this week, that's not to say it will get warm, nor is it to say winter precipitation is not a threat. All eyes will be looking at a system for Thursday-Friday.
Unlike the past couple of weeks, cold air is not for granted, so it's not a sure bet to be snow. The structure of the atmosphere will be such that we could get snow, rain, freezing rain, sleet or some wild mixture of any or all of the above from this system, and probably a few more in the near future. The absence of a really deep Arctic air mass will likely allow more moisture-bearing storm systems into our region, which means if the temperatures are just cold enough, there could be big winter weather trouble. Or just a cold rain.
Back to a regular Virginia winter. Not Minnesota or Florida.
January 23, 2003 7:50 a.m.
SOME RELIEF IN SIGHT .... BUT FIRST, MORE SNOW?
I'm sure you're not disappointed the fears of below-zero cold didn't quite pan out most places. In fact, this morning's temperature of 14 in Roanoke actually rose from about 10 late last night. Many places are in the single digits, though, and I'm sure somebody's thermometer somewhere among the hills and valleys of Southwest Virginia is registering a negative sign this morning.
The good news is that milder -- not warm, but more like normal -- weather is on its way by late next week. It may not last long as there are already signs that the Arctic Circle will make another visit to Western Virginia perhaps in two weeks. If you get cold air locked in during the critical late weeks of January it's hard to move it out entirely for the rest of winter. It just wants to hang around.
The thing about pattern changes is that the atmosphere's contortions as it changes often breed larger storm systems. Sunday poses yet another threat of snow for us and some computer models are going great guns with a much bigger storm than any of these mostly little snows that we've had. My early guess is another 2-4 inch type snow for us, maybe a little more in some areas, but there's still a lot left to be determined.
I'm keeping this short today because of other things I need to attend to, but the main thing is that we have a few more days of Arctic cold, some let up, and then the prospects of a topsy-turvy February. You didn't really think those mild, placid winters like the last several would happen every year, did you?
January 23, 2003 11 a.m.
BLUE RIDGE, MEET THE ARCTIC CIRCLE
You wonder where that extra couple of inches is that you didn't get in last Thursday night's snow? Many of you have it this morning. Some of you don't know what I'm talking about.
Some of you around western/southwestern Virginia are probably wondering "where's all that snow we were supposed to get" while others are saying "We weren't supposed to get this much." Generally, areas south and east of are coming in on the heavy side this morning, while areas north and west are light. I-81 on the west and U.S. 460 on the north seem to be good dividing lines.
I know we got bonus snow at my location in Roanoke County near the south edge of Roanoke city -- about 4 inches, after a forecast of 1. Looks more like a 2-incher here in downtown Roanoke. In a morning discussion, the National Weather Service is noting only 1/2 inch at its Blacksburg office, and an editor here says less than that fell at his home near Fincastle. Other reported amounts show up 4-7 inches in Franklin, Floyd and Patrick counties, with around an inch in the New River Valley.
An interesting development occurred last night that kept the Roanoke area, and especially places to the southeast, in some heavier snow longer than expected. As the main snow area moved east-southeast toward us from Kentucky and West Virginia, the eastern edge began eroding, and I had serious doubts about whether we would get any snow from it at all. However, radar showed a band of snow developing southeast of us, and this area intensified. In a couple of hours, it actually developed northwest toward us, while the area of snow to the west only gradually moved eastward. I was watching for the left jab and got the the right hook instead.
Apparently, this was a "moisture convergence zone" where developing low pressure to the south was able to throw some moisture back into the upper level energy approaching from the west. One weather service office south of us noted a "lee side trough," or low pressure on the east side of the Appalachians, in northwestern South Carolina that could have aided in this. Additional geographical and atmospheric factors assisted in squeezing out this moisture roughly up and down the Blue Ridge from Roanoke south to North Carolina. Whatever it was, it turned a meager snow event into a significant one at my place, while some folks expecting up to 4 inches have blades of grass poking up through the white.
Roanoke is again the dividing line today. From Roanoke west, light snow and flurries interspersed with some sunshine, with heavier snow showers in those favored upslope regions along the Virginia-West Virginia border. From Roanoke east, expect some significant snow this morning, tapering to flurries.
There will be no dividing line from the extreme cold -- everybody goes in the deep freeze tonight, with widespread single digits and probably some below-zero readings. The snowpack increases the chances of that happening. Roanoke's 33-year record low for this date of 5 degrees is in reach.
Today would not be the best day to visit the Outer Banks of North Carolina. As a surface low cranks up in the Atlantic, that area is expecting a rare heavy snow with possible near-blizzard conditions. We're starting to get some of the wind off that, and it will be blowing our freshly fallen fluffy snow around.
Blue Ridge, meet the Arctic Circle.
January 22, 2003, 8 a.m.
WESTERN VIRGINIA TUNDRA?
The snow that will probably at least whiten our ground tonight and Thursday morning is only a sideshow. Under our weather big top will be the brutal cold that will punch us in the face by Friday morning.
The National Weather Service forecast is 5 to 10 for a low Friday morning and mid-20s for a high. With the possibility of at least some snow cover and one of the deepest Arctic air masses that has come our way in almost a decade, that might be generous. Surely, if the skies clear and the winds lighten Thursday night or Friday night, someone will inherit a negative sign on their temperature reading. Don't rule it out even for Roanoke.
Our snow expected to arrive late tonight will be almost deja vu of last week's little storm -- a quick moving "Arctic wave" that will come from the northwest and then slide east across Kentucky, Tennessee, the Virginias and the Carolinas. Again, there's no deep moisture for a heavy snow, but with those liquid to snow ratios high again (15:1 expected) because it's so cold, it will take just a little bit of moisture to squeeze out a couple of inches in most places.
The danger with a storm like this is that if it comes in a little stronger than expected, and a modest amount of liquid turns into several inches of snow -- it would take only a quarter inch of liquid for about 4 inches of snow. The flip side is that it comes in weaker and only flurries occur.
Like last week, it is expected to strengthen a surface low east of us, and the Hampton Roads area is under a winter storm watch for 3-5 inches as a result. The National Weather Service call for us is 1-2 inches, 2-3 in higher elevations and areas just west and up to 6 in favorable upslope areas of West Virginia. I would say that sounds about right.
January 21, 2003
MORE LITTLE SNOWS
The computer forecast models have been doing their little back-and-forth disco again, like last week, except this time there are many dancers on the floor instead of just one.
These little upper air disturbances, called "short waves," are nightmares waiting to happen for forecasters. You bite into them too hard, like last week, and they zip away with not even enough snow to completely cover the grass. Don't bite at all, and you might be shoveling 6 inches of "30 percent chance of light snow, no accumulation."
Take today for instance: there's a chance of snow in the forecast that wasn't there until yesterday. Out of nowhere, computer models suddenly started kicking up blue and green colors over the Carolinas, edging into Virginia. A previously unheralded disturbance will sweep across as an Arctic front drops down just in time to reinforce our cold weather pattern and push away Monday's mini-thaw.
As of 11 a.m. today, there certainly wasn't much to this. Today's "storm" looks really puny. Most of the precipitation is staying down in North Carolina where it's warm enough to be mostly rain. We've had a few bouncy ice pellets here in Roanoke this morning, but it doesn't look like much more other than a few afternoon flurries. Wind and cold will prevail this week, but snow may be sparse.
Last night, the thinking was that down near the Virginia-North Carolina line, some small area might come out with 3 or 4 inches out of today's event, if it didn't mix too much with sleet, freezing rain or rain. Best chance for turf-whitening six-sided ice crystals may be in Wytheville, Galax, Martinsville and points south. Just keep an eye on the radars today to see if things don't try to push farther north.
What might be different over the next 7-10 days is signs that the subtropical jet stream is wanting to get back in the action. The subtropical jet is our moisture train from the Pacific across the Gulf of Mexico. Combine that with a cold pattern locked in by the polar jet stream and you've got a tango that could add up to big snow or ice potential. Last week, we got almost zilch Gulf moisture.
Forecasters will be watching over the next 24 hours to see if the next disturbance, scheduled to affect us Wednesday night and Thursday, will be able to get the two jet streams to do some dirty dancing over us. Not likely. Probably, this will be another vigorous but quick little pest that heads out to sea, very similar to last week's snow. Maybe another 2 inches. Maybe.
All in all, it's hard this season to get things choreographed just right for a really big snowstorm. There's still eight prime weeks of winter storm potential left, but this may be a winter with lots of little snows instead of any real big ones.
Other things to watch:
The cold air "blob," which we got a brief respite from Monday, should peak for us on Friday and Saturday, which could be a couple of frigid days, especially if there is fresh snow cover.
Another precipitation possibility over the weekend or early next week.
Questions about whether next week begins a thaw, briefly thaws then freezes hard again, or just stays frozen.
And El Nino may be gasping its last out there in the Pacific, which may mean we get less reservoir-filling precipitation through the spring than we earlier thought.
January 17, 2003
SNOW AT SEA; NOW, WE FREEZE
Our indecisive, speedy little snowstorm has zipped out to sea, leaving 2-6 inches of snow across much of our area. In its wake will be perhaps some of the coldest weather we've experienced in 7 years.
Temperatures won't push up much at all today from where they are and could fall to below zero in some sheltered valley locations tonight with a snowpack under clearing skies. Probably about 10 in Roanoke tonight.
Technically, it appears the folks who guessed 1-3 inches in our poll are the winners. Roanoke reported 2 inches officially as of 8:30 last night and probably no more than an inch fell after that point -- though at your house it's possible there is 4-6 inches. Snow fell harder and/or kept falling longer in some areas.
When the energy of the system transferred to a new coastal low pressure system, the back side of the system split apart and dissolved, so some of the final snow bands that were in Kentucky never moved through. This left behind a few peristent patches of snow late in the evening and early this morning that added an inch or two more when the snow had stopped in other places. All that's left this morning is your typical upslope snow showers in West Virginia, a few of which might manage to spit out a flake or two from time to time in the Roanoke Valley today.
This thing was a booger to watch and I think anybody involved with weather in the eastern U.S. is tired of it now. I know I am, and I actually like snow.
All through next week, there will be periodic chances of snow in a cold air regime that won't budge much. We might squeak a 40-degree Monday, but any of the rest will be lucky to hit freezing. This is that "blob" of arctic air I told you about a couple of weeks ago. Winter, an infrequent visitor since 1996, is back!
I'm going to take a break until the usual posting time on Tuesday, barring something unexpected. Late next week we may go through this whole snowstorm forecasting circus again. Stay warm and have a great weekend.
January 16, 2003 8:10 p.m.
FINALLY ...
After an incredibly topsy-turvy week of computer model runs contradicting and reversing themselves like federal judges, it is finally snowing across Western Virginia tonight, and quite heavily at times.
At this posting, it appears that we are nearing an inch at my Roanoke County location. Visibility appears to be about half a mile, and this often translates to inch an hour type snows. Considering we are likely to get 5-8 hours of snow tonight, and probably not all at quite that pace, it looks like my 4-6 inch call and the National Weather Service's 3-6 call are in good shape.
Of the 264 of you who voted yesterday and today in our snow-call poll, 34 percent thought 4-6 inches would fall. Nearly as many predicted 1-3 inches of snow.
Many locations in southeastern Kentucky are already in 3-6 inches ballpark and still snowing this evening, and those heavier bands of snow are yet to come through. Nashville, Tenn., ended up with 7 inches today.
Snow forecasting is always difficult, but I do not recall a storm that I've ever followed that threw more curve balls than this one. Once I almost pulled the trigger on jumping at a call of 7-12 inches -- not impossible yet, but probably not widespread.
Another time, I thought about pulling out of it altogether -- it never really seemed like a typical Western Virginia winter storm setup. Seeing the radar lit up like it was in Missouri this morning was the final kicker for me to hang on -- the snow was there and it had to go somewhere. And as the day wore on, the trend clearly moved in favor of a significant snowfall in Roanoke as Tennessee and Kentucky got slammed pretty good.
So enjoy or tolerate the snow. I encourage you to post your snowfall totals on our weather bulletin board.
January 16, 2003 3:45 p.m.
UN-RETREAT!
Just as was speculated here this morning, the National Weather Service in Blacksburg has retreated on its retreat -- the winter storm warning is now up for 3-6 inches in Roanoke and up to 8 in some other areas.
Sorry fellas, but you bailed on me this morning -- I held onto 4-6 while you jumped ship. The forecast's now mine to win ... or ours to lose together.
And by a narrow margin, our readers are holding on to their 4-6 inch call, too.
Expect snow by mid-evening in Roanoke, probably hard and fast.
January 16, 2003 1:30 p.m.
YO-YO IS BACK UP AGAIN
The low pressure system now appears to be coming in a little farther north than expected. I wish it would make up its mind.
The National Weather Service office in Nashville is reporting that snowfall rates are heavier than expected in west Tennessee and has upgraded its accumulation forecasts for much of central Tennessee.
The next hours are critical for us as we watch the darker colors in Tennessee that now edge up into southern Kentucky. Will that heavier precipitation continue to translate northeast and/or intensify and/or slow down a little? Any of these factors could bump up our snow totals. I expect the first to come true and possibly the second, a little. I don't think she's gonna slow down any. How much white can it lay down running by us so fast?
I'm sticking with 4-6 inches. Though 1-3 is narrowing the gap in our unscientific poll of viewers, 4-6 is still ahead there, too. Remembering, the measuring stick at the Roanoke Regional Airport is what we'll be using to determine the outcome, even though I've had issues with their snow measurements before.
The Hydrometorological Prediction Center is also now again highlighting Southwest Virginia as an area of potential heavy snow (4-8"), with hints that it might even shift a bit farther north. Click here to read the HPC's heavy snow discussion.
January 16, 2003, 8 a.m.
STILL BLURRY
I told you Monday it was going to be a gut-wrenching week for forecasters. That could still end up being the only correct forecast anybody, myself included, has made all week.
Given a series of overnight computer model runs that depict a faster, drier, more southern system than was thought just 12-18 hours ago, the National Weather Service in Blacksburg decided to pull back on snow accumulations to 2-4 inches for us tonight. Last night, the official government forecasters were touting the possibility of 4-8 inches, even hinting more at areas just to the southeast of us. The winter storm watch was canned in favor of a winter weather advisory, less ominous than a winter storm warning would have been.
A good move? If it's right, yes. But if the storm ends up being back where it was originally forecast, the retreat will be a bad gamble, and could turn into a "double retreat" if NWS decides at some point to boost snow accumulations or raise a winter storm warning. And if this thing's a total bust, this morning's move is not large enough of a retreat.
With the large area coverage of snow in the Mississippi River Valley this morning, (see radar map) the still developing nature of the storm system, the cold air mass' ability to squeeze more snow out of less moisture, the tendency for systems this winter to be stronger and track farther north and west than forecast, and a deep mistrust of computers because my Mac at work locks up 2-4 times a day (note of fairness: my PC at home fairs about the same), I probably would have left the winter storm watch up through the day simply because it is a "watch" and means the larger snow amounts are possible. They still are, if it snows hard enough fast enough this evening. Those two elements really are the crux of the matter -- how hard will it snow, how long will it snow?
At this late date, probably inside of 12 hours from when the first flakes may tumble into the Roanoke Valley (4 p.m. is my estimated starting time), I'm sorry to say this forecast is still blurry with many uncertain and perhaps even unknown factors. But that's why weather forecasting is hard -- if it were easy, it would be called sports odds making.
My probabilities are below. My lean is to 4-6 inches. So is yours, according to the poll we've been running.
January 15, 2003, 8 p.m.
IT'S REAL NOW
Well, there is a real live snowstorm under way tonight in Nebraska, Iowa and Missouri, so it is no longer a computer generated theory. It will probably even sweep down with a couple of inches as far south as my parents' house in the northeastern tip of Arkansas as it makes its way toward us tomorrow.
The National Weather Service is flying a winter storm watch for 4 to 8 inches of snow, along and southeast of a Blacksburg-Lexington line. It's almost the reverse of the usual Western Virginia snowfall map -- typically the biggest snows are in the northwest and they dwindle out as you move southeast. Blacksburg NWS seems to think Martinsville and Lynchburg have the best shot at the top end of the scale, with Roanoke maybe toward the middle and dwindling back to 2-4 inches in the mountains.
About 6 inches is my guess right now for Roanoke, and just about everybody else's too, but I admit that my instincts are that this is only a middle-of-the-road guess and that the actual event will either be much less or much more. Maybe I'll feel better in the morning, but right now I feel like the deer on the yellow line and I don't know which way to run in the headlights.
Complicating factors:
Speed of system: It's very fast to be moving from Nebraska tonight to our area in less than 24 hours. Even if it snows hard, it might snow long. On the other hand, if it slows down while it's snowing hard, it could pile up faster.
Dry snow: We might squeeze 15 inches or 20 inches of snow out of every inch of liquid, so it might not take much to pile up fast.
Track: does it go farther south of us and barely whiten the ground, or edge north and put us more in the best energy of the storm? Does it go out to sea or turn northeast along the coast and get the Atlantic Ocean involved.?
No Gulf moisture: Our major moisture source for big snows will barely be tapped, or not at all.
Strength: Does it stay steady, wind down some, or explode into a stronger system? Computer models still haven't gotten their heads together on a single answer to this.
I'll keep my probabilities the same for now (see below), as they show a combined 90 percent chance of more than an inch of snow. Your votes at last check were leaning to 4-6.
Lost in all the snow talk is tonight's very cold temperatures -- some single digits in sheltered valleys, and lots of low teens. BRRRRRRRR!
January 15, 2003, 4 p.m.
The National Weather Service has issued a winter storm watch from Thursday afternoon through Friday morning. Click here for details.
It is about that time for forecasters -- fish or cut bait. Snowstorm, light snowfall, or no.
By this evening, the National Weather Service office in Blacksburg will most likely have decided whether it will issue a winter storm watch for Thursday-Thursday night-Friday. A winter storm watch is issued if there is the potential for 4 or more inches of snow. The actual criteria varies a little from area to area, but the general idea is that if you they think you need a shovel, a winter storm watch is posted.
Computer forecast models continue to bring heavier snow to the north and west of earlier runs to the point now that much of Virginia appears as if it will get a significant snowfall. Some of the runs this morning are beginning to look like some of the more frightening scenarios speculated by some on Monday. But let's keep in mind that these are fickle silicon chips. Still, when there is a steady trend in one direction like this, that's a big concern.
Here is a factor that could boost our snow totals. Yesterday, I mentioned how cold/dry air sometimes shunted off moisture and made it hard to snow. The flip side to that is that very cold air as will be present in the upper atmosphere creates a powdery, more airy snow that "gets more bang for the buck" from whatever moisture is available. In other words, whereas the water equivalent of an inch of rain usually is worth about 10 inches of snow, the ratio could be more like 1:15 or 1:20 with our upcoming snow. So snow accumulations could be higher for less moisture content.
The Blacksburg National Weather Service office has highlighted areas along and south of Blacksburg, Roanoke and Lynchburg as the most likely areas for "heavier snow," yet to name specific numbers 36 hours out. If the north and west shift continues, this could change to encompass much of western Virginia. The NWS office in Charleston, W.Va., is calling for 2-5 inches in West Virginia; the NWS office in Morristown, Tenn., is discussing possible 3-5 inch amounts with 6-8 in the higher elevations for its counties, which include northeast Tenneseee and far southwest Virginia.
Private forecaster David Tolleris of Richmond (www.wxrisk.com) put out a forecast map Tuesday evening that puts the Roanoke area squarely in the 3-6 inch camp.
Forecasters today will be watching the Midwest to see if the storm develops as prognosticated over Nebraska and Missouri. It is then expected to dive southeast into Tennessee and turn east. The question is how far north does it track and whether it then makes another turn northeast along the coast, and if it does, how close to the coast. A strong system moving through North Carolina and then along the immediate coast could bury us.
My new probability scheme is below. If you add all the categories from 1-3 up you will see I think there's a 90 percent chance this will be a significant snow -- and I'm ratcheting up some of the larger amounts. I'm aiming at the 4-5-6 zone with increasing concern we could bust into half-foot-plus territory.
Wednesday probabilities on Thursday-Friday snow
No measurable snow 5 percent
Less than 1 inch 5 percent
1-3 inches 30 percent
4-6 inches 40 percent
7-12 inches 15 percent
12 inches or more 5 percent
January 14, 2003 (2 p.m.)
MODELS TURNING ON THE RUNWAY
A quote from a mid-morning discussion from the National Weather Service office in Wakefield, Va., translated from jargon and abbreviations: "Yesterday, the trends in the models for the end of the week potential storm in the eastern U.S. were to the south ... now trends are farther north."
The computer forecast models are making their expected northward bounce, as we discussed this morning, providing more evidence for a possible winter storm on Thursday-Friday. The goverment's Hydrometeorological Prediction Center is very much on board with the potential for a significant winter storm in our general area. The private guys pumping the storm aren't bailing out. The Weather Service offices are playing their hands well, nice middle-of-the-road game without hype they can take either way as things unfold over the next two or three days.
At last check, it was a close call between less than 1 inch, 1-3 inches, and 4-6 inches of snow in the Roanoke Valley on Thursday-Friday
And don't be surprised if a few flakes drift down on you this afternoon. Pretty feisty little disturbance coming up over the mountains at us, but the downslope flow off the mountains will rob moist of the moisture as it frequently does in the Roanoke Valley and points east. West Virginia and the highest mountain areas west of us may see an inch or two through this evening.
January 14, 2003 (9 a.m.)
TOO COLD TO SNOW? WOULD A MODEL KNOW?
Actually, the idea that is "too cold to snow" is a fallacy. But it is sometimes too dry to snow because of a cold air mass.
The big winter storm idea has taken a hit for Thursday-Friday because a lot of computer forecast models, some bullish about it 24 hours ago, show this blob of cold air on us throwing its weight around and bullying the whole weather pattern. As a result, weather systems are forced much farther south, move more quickly, and struggle to develop enough moisture in the dry air, making potential snowstorms flop around for life like a catfish on asphalt.
But meteorologists in the know, be they private or government, are not bailing on this winter storm possibility yet. The models are still showing a vigorous low pressure system moving east on Thursday-Friday across the southern United States, and the path varies from model to model, and from run to run of each model.
Maps the models spit out are really a composite or consensus of a group of maps called "ensembles," which depict about every possible scenario with a developing storm. Some of these individual ensemble maps still show big snowstorms -- and sometimes the weirdest and wildest of the ensembles is the one that comes true. Other ensemble maps show a couple of partly cloudy days -- sometimes the meekest and mildest come true.
The next 24 hours will be critical to forecasters and the fate of our Thursday-Friday snow. For one, the biggest pocket of jet stream energy that will be a culprit in this caper will move over land into British Columbia where actual physical instruments can get real readings on how strong it is and where exactly it is. Over the past few days, computer programs have been making educated guesses about it over the northern Pacific.
Secondly, forecasters will be looking for some evidence of a consistent trend in these forecast models. Computer models are not perfect. Often, they show storms several days out, kill them a few days before, then bring them back again a day or two before. I've seen things get squashed and then come back on the computer screen so much I almost want to ignore them entirely.
The National Weather Service plays it cool for a reason -- if you forecast light to start with, you can ratchet it up easier and with less reputation damage than if you forecast heavy to start with and you have to ratchet it down to nothing. That they're holding on to a 40 percent chance of snow still three days out is a sign of uncertainty, and a little higher than I expected from the guv'ment forecasters after seeing the model runs of last night. They've been through this dance too often.
So will it snow? I still say yes, but probably not the Blizzard of '03. I've learned that some of the major forecast models tend to shove things really far south in the middle range (four-five days out) then bring them steadily back to the north. That's kinda what I expect to see. The big question is moisture. This one may not tap the Gulf of Mexico the way it needs to for a big snowstorm, and the "blob" of cold air may dry it up. So many variables, so little time.
Below are some weather-geek educated guess probabilities I've worked out on how much snow we'll get in the Roanoke Valley on Thursday-Friday. I'll update these as we move through the week. They do add up to 100 percent, so there is a 100 percent chance that it will either snow or not snow.
OH, BY THE WAY ...
If you're on the mountain ridges to our west, you may get a couple of inches of snow with a weak system today. In the New River Valley, maybe a dusting here or there. In the Roanoke Valley, maybe a few snow showers.
Monday, January 13, 2003
PHASED, OR UNFAZED?
This is going to be a sleepless, gut-grinding week for many forecasters in the eastern United States, the kind of week that can make or break reputations. An intensely complicated scenario is shaping up that has the potential to produce a major, even historic, snowstorm -- but still enough uncertainty that it could dissolve into a few wind-blown flurries.
I am confident enough in what I have seen so far to say I believe it will snow measurably in Roanoke and Western Virginia on Thursday and/or Friday. I also believe, a little less firmly, that this will blow up into a major winter storm at some point. Whether we are in the major part or a minor part of all this is the big unsettled question.
The major computer models are all over the board with the specifics of this scenario, though they've come a little bit closer together than they were late last week. The big question comes down to a matter of "phasing," whether the northern and southern branches of the jet stream will work in unison, or whether they stay apart. If the former becomes true at the right time in this storm, we will be shoveling and plowing come Friday morning. If not, you might be able to just brush it off your windshield and go about your merry way.
There are separate pockets of upper level energy tracking through each branch of the jet stream. In a very vague and general sense, it's like bumper cars -- it the two run into each other, big trouble; if not, less trouble.
The various forecasting entities are playing their usual hands this morning. The National Weather Service is going conservative, noting that the major model it uses is pushing the players farther south and just brushing us. Some private forecasters are whispering things that would frighten you. I will spare you for now, since four days out this could be much ado about nothing.
Stay tuned.
Jan. 10
Will PNA + NAO = SNOW?
Would you know a PNA from a NAO if they ran smack into you? Well, they're doing just that, whether you like it or not. One is really positive and the other is negative, but they get along really well.
The positive PNA and the negative NAO are why we're in for a spell of cold weather beginning today and lasting perhaps 2-3 weeks. It could get really, really, snot-freezing cold at some point during this period, but we'll start out with just teens-20s-30s kinda stuff. The PNA-NAO square dance is also a major reason there is a stir about a potential big winter storm late next week.
The PNA is the Pacific-North American jet stream pattern. When it is in the positive phase, that means there's a high pressure system in the Pacific Ocean and lower pressure in the eastern U.S. The jet stream -- a fast-moving river of air in the upper levels that guides weather systems -- comes over the top of the high through western Canada, dives down in the middle of the United States, then sweeps south of us out into the Atlantic. This allows the cold air to come on us from Canada, while the west warms up. Reverse it, and you have the negative PNA -- low in the west, high in the east, cold in the west, warm in the east.
The NAO is the North Atlantic Oscillation. In the course of a winter, the higher and lower atmospheric pressures tend to go back and forth between the north near Greenland and the south just above the equator. In the negative phase, the high pressure is in the north and the low pressure is in the south. This causes the jet stream to buckle where it dives really deep to the south across the eastern U.S., then dramatically north and over the top of the high. Reverse it, and the jet tends to stay mild and flat across the U.S. as it squeezes between the low to the north and the high to the south.
Combine the positive PNA and negative NAO, and you lock in the cold and set up a favorable pattern for storm systems to dive into the Gulf and then sweep up the East Coast. That's exactly what is beginning to line up right now.
So, will it snow? That favorite meteorologist-weather geek game show, the Winter Storm Guessing Game, is already cranking up a full week before the potential event, right now speculated for the Wednesday-Saturday time frame of next week. (There is a little booger of a system swinging through early next week, but it should stay safely south of us.)
While certain private sector forecasters have been blowing their horn about this all week, even some last week, the government's meteorologists entered the fray yesterday with one ominous statement in the Hydrometeorological Prediction Center's daily extended forecast discussion:
"DAYS 6-7 ARE THE BIG QUESTION MARK. IN CONJUNCTION WITH OUR DEVELOPING WAVE IN THE GULF OF MEXICO...THE COLD MEAN PATTERN SUGGESTS SIGNIFICANT SN POSSIBLE FROM AR ACROSSTHE TN VLY TO THE CAROLINAS/SRN MID ATLANTIC REGION. MORE ON THIS TOMORROW..."
A developing wave in the Gulf -- snow from Arkansas across the Tennessee Valley to the Carolinas and Southern Mid Atlantic -- that's a snow track for Roanoke, Va. Often a big snow track. And then there's the question of whether it will blow up real big, run up the coast, and inherit some kind of nickname. Let's don't get ahead of ourselves.
The National Weather Service in Blacksburg added the diplomatic "chance of rain or snow" to our forecast for next Thursday. I'm going to go on the record to say that we just ain't a gonna have any above-freezing liquid in Roanoke next week. Freezing rain, maybe. Sleet, maybe. Clear but cold days with no hint of precipitation, maybe. No rain. That's my call, and I'm sticking to it, unless of course I'm wrong.
Do me a favor, though: don't clean out Kroger and Food Lion just yet. By Monday, we should have a little more data about whether there is going to be a storm or not, and sortakinda where it might go and how big it might be. This whole threat might have blown away like so many snow flurries by then.
If this thing does pan out, remember who it was that highlighted Jan. 14-17 for a signficant snow way back on Jan. 1.
Copyright 2003